Recently the interest in reducing the discharge of heavy metals into environmental waters has been spurred by rapidly rising prices for heavy metals, in particular gold and silver. Most industries that use large quantities of heavy metals, such as silver in the photographic industry, recycle used materials and attempt to recover as much metal as possible from waste waters generated during processes using those metals, such as photographic development.
Previous processes for the recovery of silver from exposed photographic film and from waste water from photographic development have suffered from limited silver extraction efficiency and from their inability to cope with the large amounts of toxic thiosulfate anions or metal-complexed cations that are by-products of photographic development. My invention is directed to the solution of both of these problems.